An artist’s impression of an electric rocket powered by an array of solar panels that can deliver 30 kilowatts. Courtesy NASA.

However, at least in broad strokes, the agency’s commitment to developing and demonstrating certain technologies it believes are critical to its future are clear, with four test missions slated for launch between 2014 and 2018 by NASA’s new Flagship Technology Demonstration program.

The first mission is a Solar Electric Propulsion test flight, scheduled for 2014–a large solar array fitted to a small unmanned spacecraft will generate 30 kilowatts of power that will be used to drive an electric rocket. The mission will last two years, first visiting a dead satellite in geosynchrous orbit to test new proximity sensors for an automated rendevous and docking system NASA hopes to build, and then the spacecraft will go on to visit a near Earth asteroid, studying it with a small set of science instruments. NASA hopes such a propulsion system will let them build efficient space tugs, or power space debris removal vehicles.

The second mission will launch a satellite that will demonstrate the ability to store cryogenic propellants such as liquid oxygen, and then transfer propellants from one spacecraft to another. The 200-day mission is targeted for 2015 and will demonstrate the technologies needed to build in-space refueling depots. Such depots could make it much easier and cheaper to send manned and unmanned spacecraft beyond low Earth orbit, as the fuel for long journeys won’t have to be brought up all in one go, meaning smaller rockets can be used.

NASA hopes to launch the third mission in 2016; this would be an inflatable habitat module more or less permanently attached to the International Space Station, similar to the modules currently being developed by Bigelow Aerospace for a private space station. In 2018, NASA would use the inflatable module as a test bed for an advanced life support system intended for long-duration manned missions.

The fourth and final mission planned would also launch in 2018, and demonstrate how NASA can use aerocapture and other techniques to land large payloads on Mars. With current technology, NASA can’t land more than 1,000 kilograms on the Martian surface at a time, far too little for a human mission. It hasn’t yet been determined if the flight test would actually take place at Mars, or if useful results could be obtained by testing the technology with Earth’s atmosphere.